Control circuit employing thermally responsive switch means



| BODDY 3,215,926

CONTROL CIRCUIT EMPLOYING THERMALLY RESPONSIVE SWITCH MEANS Nov. 2 1965- Original Filed Aug. 5, 1949 INVENTOR- Aearza. "a I a 6 United States Patent 3 215,926 CONTRGL CIRCUIT lEMPLOYING THERMALLY RESPONSIVE SWITCH MEANS Leonard Boddy, Ann Arbor, Mich, assignor to King- Seeley Thermos (30., Ann Arbor, Mich., a corporation of Michigan Application May 13, 1957, Ser. No. 658,888, now Patent No. 3,005,979, dated Oct. 24, 1961, which is a continuation of application Ser. No. 108,773 Aug. 5, 1949, now Patent No. 2,835,885, 'dated May 20, 1958. Divided and this application June 19, 1961, Ser. No. 117,864

9 Claims. (Cl. 323-68) This invention is a division of my United States patent application Serial No. 658,888, filed May 13, 1957, now Patent No. 3,005,979, which is in turn a continuation of my United States patent application Serial Number 108,773, filed August 5, 1949, now Patent 2,835,885 granted May 20, 1958.

The present invention provides an improved electric system in which a voltage regulating device delivers pulsating electric energy, at a substantially uniform effec tive voltage, from a source of alternating, pulsating, or direct current of variable voltage, to operate a load means, coupled with resistance means for continuously energizing the load means independently of the regulating device.

A preferred but illustrative embodiment of the invention is shown in the accompanying drawings, throughout the several views of which corresponding reference characters are used to designate corresponding parts:

FIGURE 1 is a diagrammatic view of a gauging system embodying the invention;

FIG. 1C is a diagrammatic view of a modified gauging system embodying the invention;

FIG. 2 is a view in top plan, on a slightly reduced scale, as compared to FIGURES 3 and 4, of a preferred construction of thermally responsive regulator;

FIG. 3 is a view in vertical section of the structure of FIG. 2, taken along the line 33 of FIG. 4;

FIG. 4 is a view in horizontal section, taken along the line 4 4 of FIG. 3; and,

FIG. 5 is a fragmentary view in vertical section, taken along the line 5-5 of FIG. 2.

It will be appreciated from a complete understanding of the present invention that the improvements thereof can, in a generic sense, be embodied in electrical control systems of widely differing types, for association with widely differing types of load circuits and widely differing types of energy supply sources. The illustrated embodiment of the present invention has been specifically designed to provide for electric gauging the engine temperature, oil pressure, and gasoline supply conditions in automotive vehicles. Such specific disclosure herein is, of course, to be regarded in an illustrative and not in a limiting sense.

Considering first the system of FIGURE 1, the illustrative gauging circuits 10, 12, and 14 are connected in parallel with each other and receive electric energy, at .a voltage regulated by regulator 16, from a source 18. The source 18 may be of various types, but when the present improvements are used in connection with automotive vehicles, source 18 may, for example, comprise a usual engine driven generator 20 and a battery 22, In line with conventional automotive practice, a voltage regulator VR is interposed between the generator and the battery and, as will be understood, serves to maintain the voltage of the latter between limits which are acceptable for many of the vehicle requirements. In practice, these limits are not close enough for satisfactory operation of desirably simple electric gauges.

The regulator 16 receives the noticeably variable output of the source 18 and delivers pulsating energy to the ice gauging circuits, the effective voltage of the regulator being substantially independent of variations in the voltage of the source. Under these conditions, it will be appreciated that the individual gauging circuits can utilize simple rheostatic elements 2.4, 26, and 28 which, in response to liquid level, engine temperature, oil pressure, or other physical condition, serve to vary the resistance of the individual gauge circuits and thereby control the current through, and consequently the positions of, the individual gauges 30, 32, and 34.

Basically, the regulator 16, as well as the other herein illustrated regulator embodiments, can be characterized as including a thermally responsive member at least a portion of which tends to move as a consequence of changes in the temperature thereof. Current modulating means are associated with this member so as to respond to the tendency to move. The current modulating means serve to increase the heating current supplied to the regulator in response to decreases in temperature thereof and vice versa. Consequently, throughout at least a predetermined range of voltages of the source, the current modulating means periodically increase and decrease the current supplied to the thermally responsive member and cause it to be maintained at a substantially uniform average temperature. On this basis, it will be appreciated that the thermally responsive member receives energy, in pulsating form, at a substantially uniform average rate. This energy rate may, of course, be expressed as E r, E being the effective or root-mean-square voltage of the energy pulsations and r being the electrical resistance of the regulator. Under any given ambient temperature condition, the electrical resistance of the regulator may, for all practical purposes, be regarded as constant. Consequently, for any given ambient temperature condition, the effective voltage of the energy pulsations absorbed by the regulator is also substantially constant and independent of variations in the voltage of the associated source of energy. The control of the effects of ambient temperature changes, as well .as the advantage which is taken thereof in accordance with certain aspects of the present invention, are discussed below.

The herein disclosed improved regulators can further be characterized in that they are adapted to have the associated gauging or load circuits connected thereto in parallel with the current consuming elements of the regulator, and subject to the current modulating means. Consequently, the load circuits also receive energy pulsations having an effective voltage which is substantially independent of variations in the source voltage. The arrangement is such that load currents have no appreciable heating effect upon the thermally responsive element. Consequently, the effective voltage established by the regulator is independent of the relative magnitudes of the heating and load currents, and the load currents may be individually varied at random without affecting in any way the action of the regulator.

As diagrammatically shown in FIGURE 1, the regulator 16 comprises a thermally responsive tri-metallic element 40, which carries a heater winding 42. One terminal of winding 42 is grounded as indicated, and the other terminal thereof is electrically connected to the element 40. In this instance the current modulating means comprises a pair of contacts 44 and 46 and a shunt resistor 70. The element 40 carries the movable contact 44, which normally engages the fixed contact 46. Contact 46 in turn is connected to the source 18 through a control switch 48 which may, for example, be controlled concurrently with or be a part of the ignition switch of the associated vehicle.

With this relation, it will be appreciated that closure of switch 48 completes the circuit from the source 18, through contacts 46-44, the body of the element 40 and the heater winding 42 to ground. Completion of this circuit supplies heat to the element 40 and causes its temperature to rise. As is discussed in more detail below, the electrical resistance of the element 40 is so low that for all practical purposes, all of the heating effect can be considered as being derived from the winding 42. With this relation, element40 can also serve as a conductor of the gauging and heating currents.

Upon being heated, the element 40 warps and separates the contacts 44 and 46, interrupting the just traced circuit and also reducing the heating effect to a value determined by shunt resistor 70. The reduction in heating effect enables the element 40 to cool and restore the contacts 44-46 to closed condition. So long, accordingly, as switch 48 remains closed, contacts 44-46 are periodically opened .and closed and the heating current is correspondingly modulated. Consequently, the element 40 acquires a temperature just high enough to hold the contacts 44-46 in a condition of incipient closing and opening. As described in connection with FIGURE 3, this critical temperature can be variously determined, as an incident to manufacture, by adjusting the position of the fixed contact 46 relative to the contact 44, so as to correspondingly determine the initial pressure between these terminals. For automotive work, it is usually preferred to adjust the regulator 16 to provide a regulated or effective voltage of about volts. Consequently, as aforesaid, and neglecting ambient effects, regulator 16 acts to receive from the source 18 an amount of electric energy, in pulsating form, which has a substantially uniform heating value. On this basis, and since, over any period of time, the wattage input to the regulator heater (E /r) is at a constant rate, it is evident that the regulator 16 breaks up the energy supplied by source 18 into a succession of pulses having an effective voltage which is independent of variations in the voltage of the source 18.

The voltage impressed across winding 42, between terminal 44 and ground is, of course, equal to the voltage impressed upon the individual gauging circuits 10, 12, and 14. These circuits, therefore are supplied from the source 18 with pulsating energy at an effective voltage which is substantially independent of variations in the voltage of the source 18. Regulator 16 thus effectively serves as a regulator of the voltage impressed across the gauging circuits, and currents drawn by the individual gauging circuits are thus independent of variations in voltage of the source 18.

In the interest of economy of manufacture, the element 40 desirably serves as a conductor of both the heating and load currents, so that the winding 42 as well as the load circuit can be directly connected to the element 40, as by a spot welding operation or otherwise. In this event, it is important, as aforesaid, that the electrical resistance of the element 40 be so low that for all practical purposes all heating effect thereon can be regarded as derived from the winding 42. In the preferred practice of the invention, the element 40 is of tri-metallic form. It may, for example, embody outer elements composed, respectively, of a material having a high coefficient of expansion, such as a comparatively high chromium alloy, and a material having a very low coefficient of expansion, such as Invar. The intermediate layer may be material such as copper or nickel having very low electrical resistance. Relative thickness of the various materials may, of course, vary. For example, a trimetallic strip having a thickness of .0095 inch may be formed of an Invar strip having a thickness of approximately .0025 inch, an intermediate layer approximately .0025 inch thick and a high coefficient outer layer approximately .0045 inch thick. The intermediate layer, being on the neutral axis of the composite strip, does not materially interfere with deflection thereof, but it does afford a good low resistance conductor through the strip. Additionally, the intermediate high conductivity layer improves the heat conductivity characteristics of the strip and increases the speed of response thereof.

In the broader aspects of the invention, any of a variety of well-known electroresponsive constructions can be employed in connection with the individual gauges 30, 32 and 34, the diagrammatically shown movable elements whereof may consequently function to commutate circuits, provide visual indications or otherwise. Preferably these gauges are of the well-known temperature compensated, thermostatic type. Each gauge employs a bimetallic element which carries a heater winding. Warping of the bimetallic element actuates an indicator needle in any well-known manner. It will be appreciated that the use of thermostatic gauges is advantageous in that they inherently have some heat capacity which can be matched with the performance of the regulator so that the individual pulsations introduced by the latter into the current supply are integrated by the gauges. In typical cases, the pulsating rate may be between 60 and pulsations per minute. The matched thermal capacities provide a synchronism of displacement of the indicator bimetal with that of the regulator following initial closure of the switch 48 and thereby provides for an accelerated pointer travel to the final point of indication, before the regulator starts its pulsing regulation of voltage. This action is desirable for quicker readings and arises from the fact that during the initial period of lag the gauges and responsive member of the regulator are subject to the full applied and unregulated voltage.

The liquid level unit 24 in FIGURE 1 is diagrammatically shown as comprising a resistor 50 disposed to be variably engaged by a grounded contact 52 which in turn is suitably connected to a float 54. As the liquid level rises, the amount of resistor 50 included in gauging circuit 10 is correspondingly reduced, which action, of course, increases the current drawn by the corresponding indicator 30. This current increase raises the temperature of its associated bimetal and causes a corresponding travel of the gauge needle. A reverse action is, of course, caused by the lowering of the liquid level.

In the temperature measuring circuit 12, gauge 32 is connected to ground through a resistor 60 having an inverse temperature coefiicient of resistance. Various materials are acceptable for this purpose, one usable material being sold under the name thermistor. Resistor 60 is, of course, located in a region the temperature of which is to be measured and changes in temperature correspondingly affect the position of the needle of the corresponding gauge 32.

In the fluid pressure responsive gauging circuit 14, the gauge 34 is connected to ground through a variable resistor, the value of which is governed by fluid pressures acting against a diaphragm 62. These pressures act through a lever 64 to adjust a contact 66 along resistor 68.

Before proceeding to a detailed description of the herein illustrated embodiments of the above diagrammatically shown elements 24, 26, and 28, it is noted that, if desired, the regulator can be so arranged that the current impulses vary gradually between finite upper and lower values instead of abruptly between a finite upper and lower value. For example, as shown in FIG. 1A, the previously described current modulating means (444670) may be replaced by a carbon pile 45, one end whereof receives a variable pressure exerted by the end of element 40. The resistance of pile 45, of course, varies inversely with the pressure exerted thereon by the element 40. In this case it will be noticed, changes in temperature of element tend to cause it to warp but may not cause an actual warpage. In FIGURE 1, on the other hand, the tendency to warpage produces a finite movement of the strip.

Alternatively, if desired, resistor 70 of FIG. 1 can be eliminated, in which event the current flow is periodically interrupted. The arrangements of FIGS. 1 and 1A introduce both upper and lower limits to the range of the voltage of the source 18 throughout which the regulator is effective. The lower limit is, of course, the voltage at which heat is supplied to the heater winding 42 at too low a rate to cause the contacts 44 and 46 to separate. The upper limit is, of course, that voltage at which the minimum current value passed through the resistor 70, is high enough to maintain the bimetallic element 40 at a temperature at which the contacts 44 and 46 are continu' ously separated. For similar reasons, the carbon pile arrangement also introduces both upper and lower limits of regulation. With the last-mentioned arrangement, in which current interruption is complete, the regulator has the above discussed lower limit of regulation, but has no upper limit of voltage regulation, except such as is imposed by the current carrying capacity of the heater Winding 42.

The system of FIGURE 1C illustrates certain of the many other variations which can, in the broader aspects of the invention, be made in the basic system of FIGURE 1. For example, it is in certain cases desirable to provide an indication, other than that afforded by the visual indicator needles, when certain of the physical conditions being 'measured reach critical or limiting conditions. More specifically, in connection with liquid level indicators, it may be desirable to provide a supplementary signal when the liquid level in the tank reaches a dangerously low limit.

In FIGURE 1C, the liquid level unit 24 is like that previously described, with the exception that it is also provided with an insulated terminal 51, disposed to be engaged by the contact 52 when the latter reaches a limiting position, in this case, the low level position. Upon being engaged, terminal 51 completes a circuit for a lamp or other indicator 53, which circuit may lead directly to the battery or may lead through the regulator 16. The direct connection is illustrated in the drawing. As will be obvious, the pressure unit 28 of FIGURE 1 may be similarly provided with one or more auxiliary contacts so as to provide for the giving of supplementary indications and these auxiliary contacts may be arranged, as will be understood, at both limits as well as intermediate positions, if desired.

In certain instances, it may be desirable to arrange the system so as to provide that some or all of the indicators will respond to physical conditions existing at dilferent points. For example, in applying the present system to engines of the dual cylinder block type, it may be desirable to arrange the temperature indicator so that it is responsive to temperature conditions in both blocks. In the system of FIGURE 1C, it is assumed that temperature conditions in the two blocks are, in general, about the same, but that an indication ought to be given if either one of the blocks reaches an undesirably high temperature' Accordingly, in FIGURE 1C, one of the engine blocks is provided with one of the aforesaid temperature indicating elements 26. The other block is provided with an auxiliary temperature unit 27, which is diagrammatically shown as comprising a bimetallic element 61 which carries a heater winding 63. The element 61 also carries a movable contact 65 which is normally separated from a grounded fixed contact 67. The unit 27 may, of course, be suitably encased so that it may be introduced into the engine block into contact with the coolant liquid. Under these conditions, element 61 assumes a temperature substantially equal to the temperature of the coolant fiuid and warps to a corresponding degree. So long as the temperature of the coolant fluid is below a predetermined critical value, contacts 65-67 remain open and the action of the associated indicator 32 is controlled entirely by the previously described temperature responsive unit 26. If, however, the temperature in the second block reaches a critical value, contacts 65-67 close and complete a circuit in parallel to that aflorded through resistor 60. The resistance of the two circuits in parallel is, of course, less than that of either circuit individually and, consequently, indicator 32 is caused to move to a full scale position,

6 clearly indicating the dangerous condition in the second block.

Proper action of the above described temperature indicating circuit 12', of course, depends upon proper balancing of the resistances of the elements 32-60-63. In a typical case, the resistance of the indicator 32 may be assumed to be approximately 15 ohms and the resistance of element 60 may be assumed to vary between 100 ohms at low temperatures and approximately 10 ohms at the upper end of the scale of indicator 32. The resistance of element 63, on the other hand, may be assumed to be between 15 and 20 ohms. Neglecting the action of the auxiliary temperature unit, the aggregate resistance of elements 32 and 60 under hightemperature conditions is 25 ohms. If, under these conditions, the second block reaches a dangerous temperature, the aggregate resistance of the network assumes a value of 21 ohms (assuming a resistance of 15 ohms for element 63), which is sufficiently low to cause the indicator needle 32 to move past the full scale reading position. The network resistance is still high enough, however, so that no undue warping of the indicator 32 is introduced.

Assuming that the blocks operate at somewhat different temperatures and that the second block is at the higher temperature, the resistance 60 will have a value in excess of 10 ohms at the time contacts 65-67 close. Under these conditions, the network resistance will be somewhat in excess of 21 ohms. As before, this will result in a movement of the needle past the full scale position, but not to an undue degree.

In unusual cases, the second block may reach a dangerous temperature at a time when the first block is at a quite safe temperature, corresponding, for example, to a resistance of 50 ohms for resistor 60. Under such conditions, the resistance of the network is approximately 26 /2 ohms which corresponds to substantially a full scale reading when the element 26 is functioning alone. Thus, by a proper selection of the relative resistance values, proper scale readings can be obtained when element 26 is acting alone; a substantially full scale reading for the second block is afforded even though the first block is at a quite low and safe temperature; and, with both blocks at a dangerous condition, a full scale reading but no undue deflection of the indicator 3%, is produced when the second block reaches the critical temperature at which contacts 65-67 close. In fact, under each of the justmentioned conditions, the range of needle movement may be confined to the range customarily marked on automotive temperature indicators as the danger zone.

A further advantage of the dual temperature indicating arrangement of FIGURE 1C is that if a warning signal is produced as a consequence of the action of the auxiliary temperature unit, this warning signal persists until the temperature of the second block has fallen substantially below the temperature which produced the signal. This is for the reason that upon closure of contacts 65-67, winding 63 is supplied with current, and supplies additional heat to bimetallic element 61. Contacts 65-67, consequently, will remain closed until the temperature of bimetallic element 61, as influenced both by ambient temperature conditions, and by the heat supplied by winding 63, falls below the critical value.

Referring now to FIGURES 2 through 5, in a preferred form, the elements of regulator 16 are mounted within a sealed enclosure constituted by upper and lower cupshaped members and 82 which may, for example, be formed of light weight metal stampings. Preferably, and as illustrated, a sealing gasket 81 is interposed between these casing members. Element 40 is illustrated as being of U-shaped form, having one leg 84 which carries the previously identified winding 42,, and a companion compensating leg 86. Leg 86 is anchored at its free end to a headed rivet 88 which serves to electrically connect leg 86 to the exposed terminal 90. It Will be appreciated that changes in ambient temperature conditions have like effects upon the two legs 8486 and cause the connecting bridge 85 to rise and fall, without (except as noted below) altering the position of the contact 44. Current flowing in winding 42, on the other hand, causes leg 84 to warp relative to leg 86 and move contact 44.

For mounting stability terminal 90 has a laterally extending, downwardly deflected leg 94 which is held in place by the companion rivet 96. Terminal 90 of FIG- URES 2 through thus corresponds to the diagrammatically shown terminal 90 in FIGURE 1.

As aforesaid, the free end of leg 84 carries the previously identified movable contact 44. The companion fixed contact 46 is carried near one end of the free leg 98 of a U-shaped spring strip 100. Leg 98 extends parallel to and is immediately above the leg 84, as viewed in FIG- URES 3 and 4. The other leg 102 of spring strip 100 is anchored to the casing by the previously identified rivet 96, and is electrically connected thereby to the companion terminal 104. Terminal 104 is diagrammatically indicated in FIGURE 1 and is provided with an upstanding lug 106 for connection to an input lead. As in the case of terminal 90, terminal 104 is provided with a laterally extending downwardly deflected leg 108 which is anchored in place by the previously identified rivet 88.

The mounting spring strip 100 for the fixed contact 46 is preformed so that it tends ,to bow downwardly as viewed in FIGURE 3 and press against the movable contact 44, thereby preloading the element 411. The free end of leg 98 of spring strip 100 cooperates with an adjustable stop 110 which limits the downward movement thereof and which, it will be appreciated, can be adjusted as an incident to final inspection to determine the amount of preloading of the bimetallic element. This adjustment determines the temperature which the regulator must attain in order to effect a separation of the contacts, and, consequently, determines the regulated voltage of the system. Adjusting screw 110 is carried by an L-shaped mounting member 112 which is carried by the rivet 88, but is insulated therefrom, as well as from the bimetallic element 40, by insulators 114 and 116.

Rivet 88 also carries, in electrical contact with the element 40, a resistor mounting clip 118. A companion clip 120 is carried by rivet 96, in electrical contact with the mounting spring strip 100, which carries the fixed contact 46. Mounting clips 118 and 120 are thus electrically connected, respectively, to the contacts 44 and 46, and may serve as a mounting for the previously identified resistor 70 of FIGURE 1. Clips 118 and 120 may also serve as a convenient means of connecting a condenser or other means across contacts 44-46, for the purpose of suppressing any tendency to cause radio interference.

As previously noted, one end of heater winding 42 is spot welded or otherwise electrically connected at 122 to the bimetallic leg 84, and the other end is correspondingly grounded to the casing 80 at 126. The casing as a whole may be mounted, and grounded, by bracket 83.

Coming now to a consideration of the effect upon the elements of the present system, of substantial changes in ambient temperature, it will be appreciated that, as aforesaid, the regulator 16 acts to maintain a leg 84 thereof at a substantially uniform average temperature, just high enough above ambient temperature to maintain contacts 44-46 in a condition of incipient opening and closing. The rate of exchange of heat between any two bodies (for example, trimetallic element 40 and its enclosing casing) is, of course, proportional to the difference between the fourth powers of the respective absolute temperatures of the bodies. On this basis, the rate of heat loss from leg 84 increases with increases in ambient temperature, and vice versa. Consequently, in order to maintain the aforesaid average temperature of leg 84, the rate at which electric energy (E /r) is supplied to winding 42 must increase with increases in ambient temperature, and vice versa.

Assuming that the resistance of winding 42 is indeor undercompensate the regulator.

pendent of ambient changes, it will be appreciated that this increase in wattage is accomplished by an increase in the effective voltage of the energy pulsations received by winding 42. More particularly, the ratio of the effective voltages at two different ambient temperatures is equal to the square root of the ratio betwen the wattage requirements of the regulator at the same two ambient temperatures.

The rising or falling effective voltage characteristic of the regulator, resulting from the increase or decrease in wattage requirements of the regulator, which accompany increases or decreases in ambient temperature can, of course, be increased by utilizing a heater winding 42 which has a positive temperature coefficient of resistance. This is because increases in resistance of the winding 42, for any given wattage requirement, must be accompanied by an increase in the effective voltage of the regulator, and vice versa.

Also, the aforesaid rising or falling votage characteristic of the regulator may be increased or decreased by adjusting the length of the compensating leg 86 relative to the length of the operating leg 84 so as to, in effect, over More particularly, if compensating leg 86 is shorter than leg 84, the regulator would, in the absence of the varying rate of heat loss occasioned by ambient changes, have a voltage characteristic which falls in response to increases in ambient temperature, and vice versa. Conversely, if leg 86 is longer than leg 84, the regulator would, even in the absence of the changed rate of heat loss, have a rising voltaige characteristic in response to increases in ambient temperature, and vice versa.

It will be appreciated, therefore, that the normal rate of change in the effective voltage of the regulator, occasioned only by the varying rate of heat loss, can be either increased, reduced or, in fact, reversed, depending upon the temperature coefficient of resistance of the winding 42 and the relative proportioning of the trimetal lic legs 84 and 86.

It will be appreciated that the wattage requirements of the gauge elements 30, 32 and 34 are affected by changes in ambient temperature in the same general sense that the regulator 16 is affected thereby. These gauge elements are shown only diagrammatically in the drawing, but it will be appreciated that they preferably embody U-shaped bimetallic elements like the element 40 and are similarly mounted. That is, one endof the compensating leg is anchored and the gauge needle responds to movement of the end portion of the other leg. A given gauge reading, of course, requires that the operating leg, which carries the associated heater winding, attain a temperature which exceeds the temperature of the compensating leg by a predetermined amount. Because of the varying rate of heat loss which accompanies changes in ambient temperature, electric enengy must be supplied to the heater winding at a corresponding variable rate in order to produce a gauge reading which is independent of the changed rate of heat loss. Assuming the heater Winding has a zero temperature coefficient of resistance, the ratio of applied voltages required to produce the same gauge reading at two different ambient temperatures is, as before, equal to the square root of the ratio of the wattage requirements at such two ambient temperatures.

In the regulator, as aforesaid, the temperature coefficient of resistance of the heater wire and the relative lengths of the compensating and operating legs can be varied rather freely to achieve a desired voltage characteristic, since the regulator does not function over a range of values, but is constrained to operate at a single position determined by the setting of the adjusting screw 110. The gauge elements, on the other hand, are required to operate over a wide range of bimetal displacement and it is preferable therefore to separately treat the two related but somewhat independent ambinet effects, i.e. the tendency to displacement of the bimetals, and the radiation losses. More particularly in the design of gauge elements it is preferred to adjust the leg lengths so that at zero readings the gauge is independent of ambient changes. Depending upon certain physical characteristics of the gauges, this compensation at zero reading may require that the operating and compensating legs be of the same or slightly different lengths. At the zero reading, the rate of energy input is of course very low and consequently radiation losses can be neglected.

For any given ambient temperature, the required operating temperature of the operating leg of the bimetallic element associated with each gauge element, of course, varies substantially between zero and full scale readings. For example, in an illustrative case, the gauging current may vary between 60 milliamperes and 200 rnilliamperes. The rate of heat loss at the high end of the scale is consequently much greater than the rate of heat loss at the low end of the scale. These differing rates of heat loss and all other variables affecting the calibration of the gauge, at any given ambient temperature, may be entirely compensated for by proper calibration of the gauge dial.

Similarly, and preferably, these effects are compensated for in the design of the associated variable resistors such as 50 or 68. As is described below in connection with FIGURES 6 through 21, these variable resistors are wound in a generally tapering form. This tapering form takes into account the fact that the movements of the associated contact fingers may not be linear with respect to the physical changes which produce them and also takes into account the aforesaid change in rate of heat loss and variables, between zero and full scale readings. This compensation thus enables the use of linear scales on the corresponding indicators.

Strictly speaking, a given percentage increase in voltage applied to a gauge element, if just sufficient to compensate, at the low end of the scale, for a given change in ambient temperature, may not quite fully compensate for the same change in ambient temperature at the full scale reading. However, any such error would be small and the design factors of the gauge may be so chosen that the compensation is closest at selected points, such as at the low end of the scale, at an intermediate point, or at the upper end of the scale; and is acceptable throughout the entire scale.

From the foregoing it will be appreciated that in a system employing several thermally responsive gauge elements, the individual gauge elements may be so designed that the same percentage change in the voltage requirements of the corresponding gauging circuits serves to at least substantially eliminate the effects of changes in ambient temperature. On this basis, and in accordance with the present invention, the regulator 16 is designed to produce this required change in its effective output voltage in response to changes in ambient temperature. In other words, the voltage characteristic of the regulator is adjusted to match the changing voltage requirements of the gauging circuits in order toat least in large part and to a commercially acceptable degree eliminate the effects of changes in ambient temperature.

It will be obvious that the foregoing remarks as to the effects of ambient temperature on the regulator 16, the control thereof, and the advantage which may be taken thereof, apply with equal emphasis to the other forms of regulators disclosed herein.

While it will be apparent that the embodiment of the invention herein disclosed is well calculated to fulfill the objects of the invention, it will be appreciated that the invention is susceptible to modification, variation and change without departing from the proper scope or fair meaning of the subjoined claims.

What is claimed is:

1. In a system for association with a source of electric energy having a variable voltage, the combination of regulating means for supplying energy from the source as a series of varying amplitude pulsations over a range of variation of the voltage of the source at a preselected rate and having a substantially constant effective voltage over a range of variation of the voltage of the source comprising a pair of normally closed electrical contacts, a polymetallic element supported at one end and controlling the position of one of said electrical contacts relative to the other and effective upon heating to move said one of said electrical contacts away from the other to open said contacts, electrically energizable heating means for said polymetallic element, electrically energizable load means energizable from said regulating means by said series of pulsations and having inherent heat capacity and integrating said pulsations and responding to the effective value of the Voltage from said regulating means, means for connecting the load means in series with said electrical contacts across the source and for connecting said heating means in series with said electrical contacts across the source for causing said electrical contacts to control the flow of current from the source through both said heating means and the load means for energizing the load means and said heating means when said electrical contacts are closed, a resistor, and means connecting said resistor in series with the load means across the source for establishing an energizing circuitfor the load means which excludes said electrical contacts for maintaining the load means continuously energized during the use of the system independently of whether said electrical contacts are opened or closed.

2. The combination of claim 1 in which said heating means and the load means are connected in parallel with one another rather than in series with one another with respect to the source.

3. The combination of claim 1 in which said resistor is also connected in series with said heating means as well as in series with the load means.

4. The combination of claim 1 in which said heating means is a resistance wire in heat transfer relation with said polymetallic element.

5. In a system for association with a source of electric energy having a variable voltage, the combination of regulating means for supplying energy from the source as a series of varying amplitude pulsations over a range of variation of the voltage of the source at a preselected rate and having a substantially constant effective voltage over a range of variation of the voltage of the source comprising a pair of normally closed electrical contacts, a polymetallic element supported at one end and controlling the position of one of said electrical contacts relative to the other and effective upon heating to move said one of said electrical contacts away from the other to open said contacts, electrically energizable heating means for said polymetallic element, electrically energizable load means energizable from said regulating means by said series of pulsations and having inherent heat capacity and integrating said pulsations and responding to the effective value of the voltage from said regulating means, means for connecting the load means in series with said electrical contacts across the source and for connecting said heating means in series with said electrical contacts across the source for causing said electrical contacts to control the flow of current from the source through both said heating means and the load means 'for energizing the load means and said heating means when said electrical contacts are closed, a resistor, and means connecting said resistor in series with the load means across the source for establishing an energizing circuit for the load means which excludes said electrical contacts for maintaining the load means continuously energized during the use of the system independently of whether said electrical contacts are opened or closed, said resistor being connected directly across said electrical contacts and in series with said heating means.

6. In a system for association with a source of electric energy having a variable voltage, the combination of regulating means for supplying energy from the source as a series of varying amplitude pulsations over a range of variation of the voltage of the source at a preselected rate and having a substantially constant effective voltage over a range of variation of the voltage of the source comprising; a pair of normally closed electrical contacts, a polymetallic element supported at one end and controlling the position of one of said electrical contacts relative to the other and effective upon heating to move said one of said electrical contacts away from the other to open said contacts, electrically energizable heating means for said polymetallic element, electrically energizable load means energizable from said regulating means by said series of pulsations and having inherent heat capacity and integrating said pulsations and responding to the effective value of the voltage from said regulating means, means for connecting the load means in series with said electrical contacts across the source dependently of whether 'said electrical contacts are opened or closed, said polymetallic element comprising a generally U-shaped element having two generally parallel legs and a cross piece connecting adjacent ends of said legs, said electrically energizable heating means for said polymetallic element differentially heating said legs.

7. In a system for association with a source of electric energy having a variable voltage, the combination of regulating means for supplying energy from the source as a series of varying amplitude pulsations over a range of variation of the voltage of the source at a preselected rate and having a substantially constant effective voltage over a range of variation of the volt age of the source comprising a pair of normally closed electrical contacts, a polymetallic element supported at one end and controlling the position of one of said electrical contacts relative to the other and effective upon heating to move said one of said electrical contacts away from the other to open said contacts, electrically energizable heating means for said polymetallic element, electrically energizable load means energizable from said regulating means by said series of pulsations and having inherent heat capacity and integrating said pulsations and responding to the elfective value of the voltage from said regulating means, means for connecting the load means in series with said electrical contacts across the source and for connecting said heating means in series with said electrical contacts across the source for causing said electrical contacts to control the flow of current from the source through both said heating means and the load means for energizing the load means and said heating means when said electrical contacts are closed, a resistor, means connecting said resistor in series with the load means across the source for establishing an energizing circuit for the load means which excludes said electrical contacts for maintaining the load means continuously energized during the use of the system independently of whether said electrical contacts are opened or closed, and manually adjustable means for elfectively adjusting the positions of said contacts relative to one another.

8. In a system for association with a source of electric energy having a variable voltage, the combination of mg ulating means for supplying energy from the source as a series of varying amplitude pulsations over a range of variation of the 'voltage of the source at a preselected vheat capacity and integrating said pulsations and responding to the effective value of the voltage from said regulating means, means for connecting the load means in series with said electrical contacts across the source and for connecting said heating means in series with said electrical contacts across the source for causing said electrical contacts to control the flow of 1 current from the source through both said heating means and the load means, for energizing the load means and said heating means when said electrical contacts are closed,

. a resistor, means connecting said resistor in series with the load means across the source of establishing an energizing circuit for the load means which excludes said electrical contacts for maintaining the load means continuously energized during the use of the system independently of whether said electrical contacts are opened or closed, and resilient leaf spring means supported at one end and resiliently supporting said other one of said electrical contacts.

9. In a system for association with a source of electric energy having a variable voltage the combination of regulating means for supplying energy from the source as a series of varying amplitude pulsations over a range of variation of the voltage of the source at a preselected rate and having a substantially constant elfective voltage over a range of variation of the voltage of the source comprising a pair of normally closed electrical contacts, a polymetallic element supported at one end and controlling the position of one'of said electrical contacts relagizable load means energizable from said regulating means by said series of pulsations and having inherent heat capacity and integrating said pulsations and responding to the eifective value of the voltage from said regulating means, means for connecting the load means in series with said electrical contacts across the source and -for connecting said heating means in series with .said electrical contacts across the source for causing .said electrical contacts to control the flow of current from the source through both said heating means and the load means for energizing the load means and said heating means when said electrical contacts are closed, a resistor, means connecting said resistor in series with the load means across the source for establishing an energizing circuit for the load means which excludes said electrical contacts for maintaining the load means continuously energized during the use of the system independently of whether said electrical contacts are opened or closed, and manually adjustable means engaging said resilient leaf spring for adjusting the effective position of said other contact relative to said one contact.

References Cited by the Examiner UNITED STATES PATENTS 1,657,816 1/28 Bonner 323-96 2,058,390 10/36 Alban et al. 200-l39 2,262,845 11/41 Hartley et a1. 32396 X 2,379,300 6/45 Hodgkins 200-122 LLOYD MCCOLLUM, Primary Examiner. MILTON O. HIRSHFIELD, Examiner. 

1. IN A SYSTEM FOR ASSOCIATION WITH A SOURCE OF ELECTRIC ENERGY HAVING A VARIABLE VOLTAGE, THE COMBINATION OF REGULATING MEANS FOR SUPPLYING ENERGY FROM THE SOURCE AS A SERIES OF VARYING AMPLITUDE PULSATIONS OVER A RANGE OF VARIATION OF THE VOLTAGE OF THE SOURCE AT A PRESELECTED RATE AND HAVING A SUBSTANTIALLY CONSTANT EFFECTIVE VOLTAGE OVER A RANGE OF VARIATION OF THE VOLTAGE OF THE SOURCE COMPRISING A PAIR OF NORMALLY CLOSED ELECTRICAL CONTACTS, A POLYMETALLIC ELEMENT SUPPORTED AT ONE END AND CONTROLLING THE POSITION OF ONE OF SAID ELECTRICAL CONTACTS RELATIVE TO THE OTHER AND EFFECTIVE UPON HEATING TO MOVE SAID ONE OF SAID ELECTRICAL CONTACTS AWAY FROM THE OTHER TO OPEN SAID CONTACTS, ELECTRICALLY ENERGIZABLE HEATING MEANS FOR SAID OLYMETALLIC ELEMENT, ELECTRICALLY ENERGIZABLE LOAD, MEANS ENERGIZABLE FROM SAID REGULATING MEANS BY SAID SERIES OF PULSATIONS AND HAVING INHERENT HEAT CAACITY AND INTEGRATING SAID PULSATIONS AND RESPONDING TO THE EFFECTIVE VALUE OF THE VOLTAGE FROM SAID REGULATING MEANS, MEANS FOR CONNECTING THE LOAD MEANS IN SERIES WITH SAID ELECTRICAL CONTACTS ACROSS THE SOURCE AND FOR CONNECTING SAID HEATING MEANS IN SERIES WITH SAID ELECTRICAL CONTACTS ACROSS THE SOURCE FOR CAUSING SAID ELECTRICAL CONTACTS TO CONTROL THE FLOW OF CURRENT FROM THE SOURCE THROUGH BOTH SAID HEATING MEANS AND THE LOAD MEANS FOR ENERGIZING THE LOAD MEANS AND SAID HEATING MEANS WHEN SAID ELECTRICAL CONTACTS ARE CLOSED, A RESISTOR, AND MEANS CONNECTING SAID RESISTOR IN SERIES WITH THE LOAD MEANS ACROSS THE SOURCE FOR ESTABLISHING AN ENERGIZING CIRCUIT FOR THE LOAD MEANS WHICH EXCLUDES SAID ELECTRICAL CONTACTS FOR MAINTAINING THE LOAD MEANS CONTINUOUSLY ENERGIZED DURING THE USE OF THE SYSTEM INDEPENDENTLY OF WHETHER SAID ELECTRICAL CONTACTS ARE OPENED OR CLOSED. 